Bags of thermoplastic film are widely used for various purposes. A common method of supplying such bags is on a roll in which the line or division between successive bags is perforated for easy detachment of individual bags. Frequently the roll of bags is mounted on a spindle for free rotation, giving rise to the risk of unrolling an excessive number of bags when one bag is detached by a sudden jerk.
A type of bag which presents the problem in exaggerated form is provided with gusseted sides. Such bags are prepared from a tube of thermoplastic film by folding a portion of the film inwardly on opposite sides, flattening the tube with its folds and sealing across the end intended to be bottom of the bag. Perforations to provide for detachment are a line spaced a short distance from the line of seal. The perforation line is through four layers of film to the extent of the gusseted sides and is therefore more resistant to detachment by a suddenly applied force.
Gusseted bags are now widely used for such purposes as "wet-pack" at supermarket checkout counters. In such uses, goods which have moisture accumulated on the surface or which tend to accumulate moisture by condensation, such as ice cream, are placed in thermoplastic film bags to protect the main packing bag and other goods packed with them. For these and other purposes it is desirable to have attractive graphics applied to the individual bags by printing while the bags are in the forming machinery.
Some of the difficulties heretofore enumerated can be relieved in part by packing the gusseted bags on a roll in a cardboard carton. It is found that, when so packed, the bags become scuffed and the graphics are smeared as the roll rotates against the bottom and sides of the carton. This difficulty occurs primarily at the ridge formed about the roll where the extra thickness occurs by reason of the inner fold of the gusset. This causes the roll to make contact with the carton along a very small area of the bag, almost line contact.